1. Field of the Invention
The present invention relates to a rotor and a torque sensor and electronic power steering system including the same.
2. Description of the Related Art
Generally, an auxiliary steering system using separate power is employed as an apparatus for ensuring steering stability of a vehicle.
Conventionally, a hydraulic apparatus has been employed as the above auxiliary steering system. Recently, however, an electronic power steering (EPS) system having a characteristic of small power loss and excellent accuracy has been used.
In the EPS system mentioned above, an electronic control unit (ECU) operates a motor according to travel conditions sensed by a speed sensor, a steering angle sensor, and a torque sensor to ensure cornering stability and to provide a rapid restoring force. Due to the above, it is possible for a driver to drive safely.
However, angular velocity as well as torque or a steering angle applied to a steering shaft must be measured to allow such a power system to intervene as a force manipulating a steering wheel.
Generally, a steering angle sensor is used to measure a rotation angle of the steering shaft and a torque sensor is employed for measuring steering torque.
Recently, however, a torque angle sensor (TAS) which can sense torque and a rotation angle simultaneously has been widely employed. However, since a process of manufacturing a TAS which detects a steering angle or steering angular velocity is complicated and there is high probability of a failure or malfunction of the TAS, a torque index sensor (TIS) adopting a principle of an index sensor is sometimes used.
Meanwhile, a magnet which is commonly employed in the TAS and the TIS is formed in a ring shape and is fixed to a yoke by bonding so that vertical movement of the magnet may be regulated.
However, when the magnet is fixed in only a vertical direction and a crack is generated on the magnet or the magnet is broken due to an external shock, the broken magnet can be deviated in a circumferential direction thereof so that the magnet deviates from an installation location thereof. There is a risk of the deviated magnet damaging other sensors installed around the magnet and the damaged magnet not forming a magnetic field normally, and thus there is a problem in that it is impossible to measure the torque of the steering shaft.